Technical Field
The present invention relates to a composition for manufacturing contact lenses. More particularly, the present invention relates to a composition for manufacturing contact lenses comprising hydrophilic siloxane macromer.
Description of Related Art
The hydrogel contact lenses are made from hydrogel materials, such as poly-2-hydroxyethyl methacrylate (p-HEMA), and the strength of 2-hydroxyethyl methacrylate (HEMA) can be improved by adding crosslinking agent like ethylene glycol dimethacrylate (EGDMA). Since the water content of the HEMA is only about 38.8%, the hydrophilic monomer, for example N-vinylpyrrolidone, N,N-dimethylacrylamide and methyl acrylic acid, is added to improve the water content of such materials for the contact lenses. With the addition of the hydrophilic monomer, the water content of the contact lenses can increase up to 80%. However, the higher water content of the contact lenses is, the lower tension and toughness thereof become. The water content of contact lenses generally ranges from about 45% to 58%, but the real oxygen permeability can only reach about 15-35 regardless the further improvement of the water content.
Silicone hydrogel contact lenses have better oxygen permeability than hydrogel contact lenses. Silicone hydrogel contact lenses comprises a silicone polymeric material which was made by polymerizing two siloxane macromers, which have different chemical structures and different molecular weights, and a hydrophilic monomer, such as N-vinylpyrrolidone (NVP), methyl acrylic acid and N,N-dimethylacrylamide.
However, because of the hydrophobic characteristic on the surface of silicone hydrogel contact lenses, it is apt to incur the bacteria breed and eyes irritation. Therefore, an object of the present invention is to provide a composition of contact lenses and a method for manufacturing contact lenses by using the same to surmount the aforesaid disadvantages of the prior art.